1. Field of the Invention
The present invention relates to a method and a device for sealing a ceramic package of a SAW (Surface Acoustic Wave) filter, in which when making a ceramic package of an environmentally sensitive SAW filter such as a SAW duplexer filter or a SAW filter, a first sealing is carried out between a ceramic main body and a metal case so as to protect the chip component, and then, a second sealing is also carried out between the ceramic main body the metal case, so that the shielding effect against external electromagnetic fields would be superior, and so that the costs are reduced and so that workability can be improved, and so that the sealing can be made more secure.
2. Description of the Related Art
In the generally known conventional ceramic packaging, an air-tight status is maintained so that the environmentally sensitive various semiconductors or SAW filters or SAW duplexer filters can be protected from the external influences, and so that gas or moisture would not be generated within the ceramic package, thereby protecting the internal chip component.
Such a ceramic package for the conventional SAW filter is illustrated in FIG. 1. As shown in this drawing, a solder ball is disposed within a chip installing part 20 of a ceramic main body 10, so as to install a chip component 40. Alternatively, a conductive bond 30 or an ultraviolet ray-cured bond is spread on the bottom of the chip component 40 to carry out a bonding, and thus a chip wire 50 is drawn, thereby realizing an electrical connection through a bonding.
Furthermore, a metal case 70 is mounted upon the ceramic main body 10, and a surface electrode layer 80 made of Ag and a brazing material 60 made of Au/Sn are disposed between the metal case 70 and the ceramic main body 10, thereby carrying out a heat bonding.
In this conventional ceramic package constituted as described above, the chip component 40 is installed through the solder ball to the chip installing part that is installed within the ceramic main body 10, and then, it is electrically and mechanically secured. Alternatively, a conductive bond 30 or an ultraviolet rayxe2x80x94cured bond or the like is spread on the bottom of the chip component 40, and then, a chip wire 50 made of Au or Al is drawn, thereby electrically connecting the chip component 40.
A surface electrode layer 80 made of Ag is formed on the surface of the ceramic main body 10, and then, in order to seal off the chip component 40 of the ceramic main body 10, a brazing material made of Au(80%)/Sn(20%) is disposed between the metal case 70 and the main body 10. Then a heating is carried out at 300xcx9c800xc2x0 C. for 5-10 minutes under an N2 atmosphere, thereby sealing the package.
However, during the sealing operation, when working on the brazing material 60 for heat-bonding the Ag electrode layer 80 on the ceramic main body 10, the baking is carried out at a temperature of about 300xcx9c800xc2x0 C. under an N2 atmosphere, and therefore, the main body 10 which had already been baked is reduced and is made brittle. Further, a gas is introduced into the chip package, thereby adversely affecting the quality of the chip package.
Furthermore, the surface electrode layer 80 of the ceramic main body 10 makes it impossible to maintain an air-tight state due to the non-uniformness of the heat bonding. Furthermore, the brazing material is too expensive, and therefore, the manufacturing cost is increased.
The present invention is intended to overcome the above-described disadvantages of the conventional technique.
Therefore it is an object of the present invention to provide a ceramic package sealing device for a SAW filter, in which in order to protect the chip component within the ceramic main body, first and second sealing are carried out between a metal case and the ceramic main body so as to prevent an internal contamination, and so as to improve the shielding effect against external electromagnetic fields.
It is another object of the present invention to provide a method for sealing a ceramic package of a SAW filter, in which any gas generation from an epoxy resin or the like is prevented during the first sealing so as to prevent any quality degradation due to the presence of the gas, and through the second sealing, a baked curing becomes unnecessary so as to improve the sealing quality by the normal temperature curing, thereby achieving a reduced cost and an improvement of the workability.
It is still another object of the present invention to provide a method for sealing a ceramic package of a SAW filter, in which a paste adhesive is used during the sealing operation, so that a uniform sealing can be formed regardless of the surface conditions of the ceramic main body and the metal case.
In achieving the above objects, the device for sealing a ceramic package of a SAW filter according to the present invention includes: a ceramic main body with a chip installing part formed within it, for installing a chip component;
a first sealing part consisting of: a step formed on the ceramic main body; and a first bonding means, for securing a metal case by it; and
a second sealing part consisting of: a surface electrode means and a second bonding means, for bonding the metal case and the ceramic main body together.
In another aspect of the present invention, the device for sealing a ceramic package of a SAW filter according to the present invention includes:
a ceramic main body with a chip installing part formed within it, for installing a chip component;
a first sealing part consisting of: a step formed on the ceramic main body, a surface electrode layer, and a first bonding means for securing a metal case; and
a second sealing part consisting of: a second bonding means for making the metal case bonded to the ceramic main body.
In still another aspect of the present invention, the method for sealing a ceramic package of a SAW filter according to the present invention includes the steps of: i) preparing a ceramic main body with a chip component installing part formed within it; ii) forming a surface electrode layer on the ceramic main body; iii) securing a chip component and a chip wire on the chip component installing part of the ceramic main body; iv) carrying out a first sealing between the ceramic main body and the metal case; and v) carrying out a second sealing between the ceramic main body and the metal case integrally with a surface electrode layer of the ceramic main body.